OR-732 add user notification directive for community invitation response (accept or decline)
OR-732 improve user notification display
OR-732 tests for communityMembershipInvitationNotification directive
OR-732 improve error handling for rest calls
OR-732 change template displayer to use correct user-notification category
OR-732 add missing i18n call in template
Merge pull request #511 in OR/rse from OR/rse-gcrosmarie:OR-732-community-membership-accept-decline-directive to master

* commit '902baef20cef328438760434e538d38eee386071':
  OR-732 add missing i18n call in template
  OR-732 change template displayer to use correct user-notification category
  OR-732 improve error handling for rest calls
  OR-732 tests for communityMembershipInvitationNotification directive
  OR-732 improve user notification display
  OR-732 add user notification directive for community invitation response (accept or decline)